KR20220015035A - Manufacturing method of subframe for automobiles using tailored weld blank by plasma welding - Google Patents

Abstract

The present invention relates to a method for manufacturing a subframe for an automobile using a tailored weld blank by plasma welding. The present invention is to reduce influence of a heat affected zone of welding so that deformation of a material is reduced. The method for manufacturing the subframe for the automobile using the tailored weld blank by the plasma welding of the present invention comprises: (a) a blanking process; ⒝ an installation process; ⒞ a welding process; ⒟ an inspection process; ⒠ a molding process; and ⒡ a bonding process.

Description

Manufacturing method of subframe for automobiles using tailored weld blank by plasma welding

The present invention relates to a method for manufacturing a subframe for an automobile using a tailored weld blank by plasma welding, and more particularly, to a method for manufacturing a subframe for an automobile using a plasma welding method using plasma after cutting different steel sheets having the same thickness or different thicknesses and materials. It relates to a method for manufacturing a subframe for an automobile in which a subframe for an automobile is manufactured using a tailored weld blank for a subframe for an automobile through a process of welding and then molding by a press.

In general, the sub-frame used in a vehicle is located at the bottom of the vehicle to support the suspension and powertrain parts, and reduces vibrations generated in the powertrain and vibrations generated from the road surface from being transmitted to the vehicle body. It plays a role in protecting the engine and driver in case of impact from the side.

As described above, the conventional method of manufacturing a dissimilar material sub-frame used in a vehicle body is disclosed in Korean Patent Registration No. 10-1813949 (announcement date January 03, 2018) by using a steel plate formed of a steel material to form an upper panel and a lower panel. Arc welding and press working to produce the center panel 110, placing the center panel 110 in the casting mold, and then introducing the aluminum material into the casting mold using the aluminum casting method of the center panel 110 A step of generating the side panels 120 and 130 formed of an aluminum material including the coupling blocks 123 and 133 into which the side surfaces are inserted, and the friction stir welding apparatus 300 on the upper and lower portions of the coupling blocks 123a and 133a, respectively. A method of manufacturing a dissimilar material sub-frame is known by fusing the center panel 110 and the side panels 120 and 130 by using friction stir welding.

However, the conventional dissimilar material sub-frame manufacturing method uses an aluminum casting method to produce the side panels 120 and 130, so the manufacturing process is complicated, and the center panel 110 and the side panels 120 and 130 are friction-stirred. By welding, the strength of the sub-frame 100 to which the center panel 110 and the side panels 120 and 130 are fused is weakened, and since the price of aluminum is higher than that of the steel plate, there is a problem in that the manufacturing cost is high.

Korean Patent Registration No. 10-1813949 (Announcement date January 03, 2018) Title of Invention: Dissimilar material sub-frame and dissimilar material sub-frame manufacturing method

The method of manufacturing a subframe for automobiles using a tailored weld blank by plasma welding of the present invention is manufactured by plasma welding steel sheets of the same or different thickness and the same or different materials to each other and plasma welding, The range of weldable plate thickness is wide, and the cost is lower than that manufactured by laser welding, and the dynamic stiffness is excellent. In order to prevent deterioration of welding quality due to oxidation when exposed to the air when the bead temperature is high, it is a technical task to improve welding quality by putting a shield gas into the back of the welding.

In order to solve the above technical problem, the method for manufacturing a sub-frame for a vehicle using a tailored weld blank by plasma welding of the present invention is: The front sub-frame upper panel composed of the left side member, the front cross member, and the rear cross member, and the steel plate having the same thickness or different thicknesses and materials are cut to a predetermined size and cut to the right side member, the left side member, and the front cross member , a blanking process of cutting the lower panel of the front sub-frame made of the rear cross member; ⒝ Install front and rear cross members of the upper panel between both ends of the right and left side members of the upper panel cut by the blanking process (A), and front cross between the upper ends of the right and left side members of the lower panel a member installation process of installing a member and installing a rear cross member at the bottom; ⒞ In the upper panel installed in the member installation step, the front and rear cross members are installed at both ends of the right and left side members of the upper panel, and at the right and upper ends of the left and right side members of the lower panel, and at the bottom of the right and left side members. Plasma welding process in which plasma welding is performed on the bonding area of the front and rear cross members to be installed; ⒟ In the plasma welding step, the welding part inspection process of the panel by measuring and inspecting the welding part of the upper panel and the lower panel joined by plasma welding; ⒠ a press forming process of forming an upper panel and a lower panel that have passed the panel welding site inspection in the panel welding site inspection process with a press; ⒡ It is characterized in that it is manufactured through the upper panel and lower panel combining process: where the upper panel and the lower panel, which have undergone the forming process by the press, are added (overlaid) and joined by CO2 welding.

In the plasma welding, the front and rear cross members 3 and 4 and the right and left side members 1 and 2, which are the material of the upper panel 20, have a clamp pressure of 0.7 to 0.8 mega Pascal (MPa). Clamp, welding current 165 amps (A), welding speed 55 cm/min, plasma (Pilot) gas is used by mixing argon gas (Ar) and hydrogen gas (H2), shield gas is argon 100% of gas (Ar) and 100% of argon gas (Ar) are used for the rear gas, and the gap between the front and rear cross members (3) (4) and the right and left side members (1) (2) is 0.15. mm or less, the standoff distance is 3 mm, the working angle of the torch is 15 degrees, the traveling angle is 10 degrees, and the welding part inspection of the plasma welding is T/To ≥ 0.8, Reference plane step (C) is for upper panel: 0.32mm or less, lower panel: 0.36mm or less, welding bead unevenness (A) is within ±0.25mm, and the opposite side of welding bead concavity (B) is 0 ≤ B ≤ 1mm Within, the undercut is characterized by meeting ≤ 0.1mm, no blow hole and no welding hole.

According to the present invention, the members of the upper panel and the lower panel of the same or different thickness and the same or different materials are plasma-welded by placing the members of the upper panel and the lower panel cut by a tailored blank, then forming the upper panel and the lower panel with a press. By attaching the upper and lower panels to the manufacturing by CO2 welding, the range of weldable plate thickness (0.5 ~ 6.0mm) can be widened, and the cost is lower than that manufactured by laser welding, and the movement of the vehicle It has excellent dynamic stiffness to withstand the torsional strength in this state, and the weld quality of the weld joint is excellent and the effect of the heat affected zone is small, so the deformation of the material is significantly reduced.

1 is a plan view showing a conventional heterogeneous material sub-frame.
Figure 2 is a flow chart showing a conventional method for manufacturing a dissimilar material sub-frame.
Figure 3 is a process diagram of the front sub-frame upper (Upper) panel and the front sub-frame lower (Lower) panel of the present invention.
4 is a flowchart showing a method for manufacturing a sub-frame according to the present invention.
5 is a plasma welding operation diagram according to the present invention.
6 is a schematic diagram of an inspection apparatus for inspecting the plasma welding site of the present invention.
7 is a view showing a welding portion after plasma welding according to the thickness of the present invention.

First, the term tailored blank (TB) applied in the present invention refers to a material cut by cutting steel sheets having different thicknesses, strengths, materials, etc. to an appropriate size and shape, and tailored weld blank (Tailored Weld Blank). : TWB) means a member in which two or more materials (steel plates) having the same or different thickness or material cut by a tailored blank are buttted to each other and welded.

The front subframe using a tailored weld blank according to the present invention is made by combining an upper panel and a lower panel using a tailored blank by plasma welding as shown in FIG. 3, and the upper panel and the The manufacturing method of the front subframe by coupling to the lower panel is a manufacturing process diagram of the upper panel of the front subframe and the lower panel of the front subframe using the tailored weld blank of the present invention shown in FIG. 3 and the present invention of FIG. It will be described with reference to the manufacturing process diagram as follows.

First, ⒜ In order to manufacture the subframe 10 using the tailored weld blank in which the upper panel 20 and the lower panel 30 using the tailored blank are combined, the sub frame is made of steel sheets having the same thickness or different thicknesses and materials. The four pieces corresponding to the components of the upper panel 20 placed on the upper part of (10), namely, the right side member (1), the left side member (2), the front cross member (3), and the rear cross member (4) After cutting to a predetermined size, the blanking is cut by a cutting press, which is the blanking process (A).

And, the prepared steel sheet having the same thickness or different thicknesses and materials, the right side member (1'), the left side member (2') corresponding to the components of the lower panel 30 placed under the subframe 10, After cutting the front cross member 3' and the rear cross member 4' to a predetermined size, the blanking is cut by a cutting press, which is the blanking process (A).

After the blanking cut, in order to improve the welding quality, the burr must be completely removed from the blanked cut surface, and contaminants such as foreign substances must be completely removed. make it larger than %.

⒝ The front and rear cross members (3) (4) of the upper panel (20) are placed between the right and left side members (1) (2) of the upper panel (20) cut and formed by the blanking process (A). The right and left side members of the lower panel 30 fixed by the clamp 6 installed on the jig 5 and cut by the blanking process (A) on the clamp 6 installed on the jig 5 . The front cross member 3' is fixedly installed between the upper ends of (1') and (2'), and the rear cross member 4' is fixedly installed at the lower end to complete the member installation process (B).

⒞ In the member installation step (B), the front and rear cross members 3 Plasma welding is performed on the joint where ) (4) is installed, and plasma welding is performed so that the front and rear cross members (3, 4) are joined to both ends of the right and left side members (1) and (2) of the upper panel (20). Complete step (C).

And, the upper both ends of the right and left side members 1' and 2' of the lower panel 30 fixed to the clamp 6 installed on the jig 5, and the right and left side members 1' and 2 '), plasma welding is also performed on the bonding site of the front and rear cross members 3' and 4' installed at the lower end of the lower panel 30 to both ends of the right and left side members 1' and 2' of the lower panel 30. The plasma welding process (C) is completed so that the front cross member 3' is joined to the lower ends of the right and left side members 1' and 2', and the rear cross member 4' is coupled to the front cross member 3'.

At this time, the plasma welding of the plasma welding process (C) is, as an example, as shown in FIG. 5 , fixed to the clamp 6 installed on the jig 5 to illustrate plasma welding, and the upper panel 20 This indicates that the front and rear cross members 3 and 4 with a thickness of 1.6 t are plasma-welded to the right and left side members 1 and 2 with a thickness of 3.2 t.

The upper panel 20 clamps the right and left side members 1 and 2 having a thickness of 3.2t different from each other in thickness t and the front and rear cross members 3 and 4 having a thickness of 1.6t (6). and then welded with a plasma welding machine. The lower panel 20 has the same thickness of 1.8t right and left side members (1') (2') and the front and rear cross members (3') of 1.8t thickness. After fixing (4') with the clamp (5), it is welded with a plasma welding machine. At this time, oxidized scale is generated on the rear side of the weld and deteriorates the welding quality. make it

Clamps (5) the right and left side members (1) and (2) of the upper panel (20) having different thicknesses (t) of 3.2t and the front and rear cross members (3) and (4) of the thickness of 1.6t (5) After fixing with plasma welding machine, the material of the front and rear cross members (3) (4) and the right and left side members (1) (2) are clamped at a clamping pressure of 0.7 to 0.8 megapascals (MPa), The welding current is 165 amps (A), the welding speed is 55 cm/min, and the plasma (Pilot) gas is a mixture of argon gas (Ar) and hydrogen gas (H2).

And, 100% argon gas (Ar) is used for the shield gas, and 100% argon gas (Ar) is used for the rear gas. In 1)(2), the gap should be 0.15 mm or less, the standoff distance should be 3 mm, and the working angle of the torch should be 15 degrees and the traveling angle should be 10 degrees for welding.

Then, the right and left side members (1') (2,) and the front and rear cross members (3') (4') having the same thickness (t) of the lower panel 30 are 1.8t with the clamps 5 ), and welding with a plasma welding machine, the clamp pressure of the front and rear cross members (3') (4') and the right and left side members (1') (2') is 0.7 ~ 0.8 Megapascal (MPa). ), the welding current is 125 amps (A), the welding speed is 60 cm/min, and the plasma (Pilot) gas is a mixture of argon gas (Ar) and hydrogen gas (H2), and shield gas 100% of argon gas (Ar) is used, and 100% of argon gas (Ar) is used for the rear gas, and the gap between the front and rear cross members (3) (4) and the right and left side members (1) (2) is 0.15 mm or less, the standoff distance is 3 mm, and the working angle of the torch is 0 degrees and the traveling angle is 5 degrees to perform welding.

In the plasma welding of the lower panel 30 , only a welding current, a welding speed, a working angle of the torch, and a traveling angle are different from the upper panel 20 .

Plasma welding conditions applied to the present invention are shown in the table below.

division upper panel lower panel welding current 165 amps (A) 125 amps (A) welding speed 55 cm/min 60 cm/min clamp pressure 0.7 to 0.8 MPa 0.7 to 0.8 MPa Plasma (Pilot) gas Argon gas (Ar) and hydrogen gas (H2) Argon gas (Ar) and hydrogen gas (H2) Shield gas Argon gas (Ar) 100% Argon gas (Ar) 100% back gas Argon gas (Ar) 100% Argon gas (Ar) 100% The gap between the front and rear cross members and the right and left side members 0.15 mm or less 0.15 mm or less standoff distance 3 mm 3 mm working angle of the torch 15 degrees 0 degrees Torch travel angle 10 degrees 5 degrees

The tailored weld blank manufactured by plasma welding of each member cut by the blanking process is manufactured by using one selected from the group consisting of steel sheets such as general steel sheets and high tensile strength steel sheets.

⒟ In the plasma welding step (C), the thickness of the welded portion according to the welding area of the upper panel 20 and the lower panel 30 joined by plasma welding is reduced, the reference plane step, the amount of weld bead 凹, the presence or absence of the bead concave on the opposite side of the welding, the under The cut is measured, and the panel's welding part inspection process (D) is performed to inspect blowholes and welding holes.

The welding part inspection process (D) of the panel is a plasma welding part welded with the same thickness of (a) of FIG. 7 and a plasma welding part welded with a different thickness of (b) as reference, the base 10 and The gap between the upper panel 20 and the lower panel 30 placed on the upper part of the base 10 is 0.25 mm or less, and the weld bead is inspected with the CCD camera inspection equipment 11, and the weld bead is “T/To: Welding part thickness reduction, To: base material thickness, T: thickness reduction part, T': thickness reduction part, C: reference plane step, A: welding bead burrow, B: welding bead convexity" Weld thickness reduction (T/To) is T/To ≥ 0.8, reference plane step (C) is for upper panel: 0.32 mm or less, lower panel: 0.36 mm or less, weld bead unevenness (A) is ±0.25 Within mm, the presence or absence of bead concavity (B) on the opposite side of welding is within 0 ≤ B ≤ 1 mm, undercut is ≤ 0.1 mm, and there is no blow hole or weld hole.

The criteria for determining the plasma welding area are shown in the table below.

Item Mark Criteria Reduction of weld thickness T/To T/To ≥ 0.8 reference plane step C Upper panel: 0.32mm or less
Lower panel: 0.36mm or less Weld Bead Weight A Within ±0.25mm Presence or absence of bead 凸 on the opposite side of welding B 0 ≤ B ≤ 1mm undercut ≤ 0.1mm blow hole there won't be weld hole there won't be

⒠ The upper panel 20 and the lower panel 30, which satisfy the welding site inspection of the panel in the panel welding site inspection process (D), are formed by pressing, which is the forming process (E).

Then, ⒡ the upper panel 20 and the lower panel 30, which have undergone the press forming process (E), are added (overlaid) and joined by CO2 welding, and through the upper and lower panel bonding process (F), the plasma of the present invention A subframe for automobiles using a tailored weld blank by welding will be manufactured.

Therefore, the subframe for automobiles using the tailored weld blank by plasma welding of the present invention manufactured through each of the above manufacturing processes has a lower cost compared to that manufactured by laser welding, and when installed in a vehicle and operating a vehicle The dynamic stiffness is excellent to withstand the torsional strength in the state of vehicle movement, and the welding quality of the weld joint is excellent, so the effect of the heat affected zone is small, and the deformation of the material is significantly reduced.

10 ; Sub frame 20: upper panel 30: lower panel
1, 1' : Right side member, 2, 2' : Left side member
3, 3' : Front cross member 4, 4' : Rear cross member
5: jig 6: clamp 7: working angle
8: travel angle 9: stand-off distance 10: base
11: CCD camera inspection equipment

Claims (3)

⒜ Prepared steel sheets of the same thickness or different thicknesses and materials, cut to a predetermined size and cut to consist of a right side member (1), a left side member (2), a front cross member (3), and a rear cross member (4) The front sub-frame upper panel 20 and the right side member (1'), the left side member (2'), the front cross member (3 '), a blanking process (A) of cutting the front sub-frame lower panel 30 made of the rear cross member 4';
⒝ Clamp the front and rear cross members 3 and 4 of the upper panel 20 between both ends of the right and left side members 1 and 2 of the upper panel 20 cut by the blanking process (A). (5), the front cross member (3') between the upper ends of the right and left side members (1') and (2') of the lower panel 30 is fixed to the clamp (5) and installed at the lower end There is a member installation process (B) for installing the rear cross member (4');
⒞ The part where the front and rear cross members 3 and 4 are installed at both ends of the right and left side members 1 and 2 of the upper panel 20 installed in the member installation step (B), and the lower panel ( 30), the front and rear cross members 3' and 4 installed at the upper ends of the right and left side members 1' and 2' and at the lower ends of the right and left side members 1' and 2'. Plasma welding process (C) for joining by plasma welding on the bonding site of ');
⒟ a welding part inspection process (D) of the panel measuring and inspecting the welding parts of the upper panel 20 and the lower panel 30 joined by plasma welding in the plasma welding step (C);
⒠ a press forming process (E) of forming the upper panel 20 and the lower panel 30 that satisfy the welding site inspection of the panel in the panel welding site inspection process (D) with a press;
⒡ Upper panel and lower panel combining process (F) in which the upper panel 20 and the lower panel 30, which have undergone the forming process (E) with the press, are added and joined by CO2 welding:
A method of manufacturing a subframe for a vehicle using a tailored weld blank by plasma welding, characterized in that it is manufactured through The method of claim 1,
In the plasma welding, the front and rear cross members 3 and 4 and the right and left side members 1 and 2, which are the material of the upper panel 20, are clamped at a clamping pressure of 0.7 to 0.8 megapascal (MPa), , welding current of 165 amperes (A), welding speed of 55 cm/min. Plasma (Pilot) gas is a mixture of argon gas (Ar) and hydrogen gas (H2) Ar) 100%, argon gas (Ar) 100% is used for the rear gas, and the gap between the front and rear cross members (3) (4) and the right and left side members (1) (2) is 0.15 mm or less , A method of manufacturing a subframe for automobiles using a tailored weld blank by plasma welding, characterized in that the standoff distance is 3 mm, the working angle of the torch is 15 degrees, and the traveling angle is 10 degrees. 3. The method according to claim 1 or 2,
In the welding part inspection of the plasma welding, the thickness reduction (T/To) of the welding part is T/To ≥ 0.8, the reference plane step (C) is the upper panel: 0.32 mm or less, the lower panel: 0.36 mm or less, the amount of concavo-convex of the weld bead (A) is within ±0.25mm, the presence or absence of a bead on the opposite side of welding (B) is within 0 ≤ B ≤ 1mm, undercut is ≤ 0.1mm, and the absence of blowholes and welding holes by plasma welding, characterized in that A method for manufacturing subframes for automobiles using tailored weld blanks.

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